He is also an adjunct associate professor in the university's Department of Psychology and a chief of neurosurgery at Seton Brain and Spine Institute. "Our hypothesis is challenging the definition of a universal spatial scale of environment predominant in lower mammals, which may open up important avenues of discovery," said Robert Buchanan, another lead author on the study and an associate professor at Dell Medical School. "They not only confirm a previous report but extend the findings by showing that the size of the neuronal representation by entorhinal grid cells scales with the environment," Buzsáki said.
This study is one of the few on human subjects that report on the activity of individual neuron behavior, said György Buzsáki, an expert from New York University Medical Center who was not involved in the research. Due to the differences discovered between the human and rodent systems of navigation, the researchers emphasize that generalizing results from studies on animal subjects may provide inaccurate conjectures. The study builds on earlier Nobel Prize-winning research exploring the entorhinal cortex of rodents.
Deeper knowledge of these neuronal mechanisms can inform the development of techniques to prolong the health of this part of the brain and combat diseases such as Alzheimer's. The findings illuminate the fabric of the human memory and spatial navigation, which are vulnerable to disease and deterioration. The nature of the coordinate system differs between humans and rodents - Cartesian and hexagonal respectively. In contrast, rodents do so relative to the walls of the environment through physical exploration. When seeking navigational cues in any given location, humans automatically align their internal compass with the corners and shape of the space. This flexibility differs from rodents' rigid map that has a constant grid scale and empowers humans to navigate diverse places. Humans rescale their internal coordinate system according to the size of each new environment. By measuring their brain activity, the researchers identified three previously unknown traits of the system: Patients performed a virtual navigation task on a tablet computer in four environments daily for seven to eight consecutive days. (The brains of individuals with epilepsy function normally when not undergoing a seizure.) Neurons there serve as the internal coordinate system for humans. Through a partnership with Seton Healthcare Family, the researchers in the UT Austin Human Brain Stimulation and Electrophysiology Lab were able to measure relevant brain activity of epileptic patients whose diagnostic procedure requires that they have electrodes planted in the entorhinal cortex of the brain. So, it's vital that we continue to further our understanding of this part of the brain," he said. "Dysfunction in this system causes memory problems and disorientation, such as we see in Alzheimer's disease and age-related decline. Nadasdy is also a researcher at Eötvös Loránd University and the Sarah Cannon Research Institute at St.
"Our research, based on human data, redefines the fundamental properties of the internal coordinate system," said Zoltan Nadasdy, lead author of the study and an adjunct assistant professor in the university's Department of Psychology. The way humans navigate their surroundings and understand their relative position includes an environment-dependent scaling mechanism, an adaptive coordinate system with differences from other mammals, according to the study led by researchers at The University of Texas at Austin. Whereas humans can look at a complex landscape like a mountain vista and almost immediately orient themselves to navigate its multiple regions over long distances, other mammals such as rodents orient relative to physical cues - like approaching and sniffing a wall - that build up over time.
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